All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Norman Cook: There is engineering works at Emley Moor which might interrupt television broadcasts. We have had reports from people using Emley who've had interruption to ITV etc.
As Dronfield transmitter receives its signal off-air from Emley then maybe at times the signal from Emley isn't good enough for it.
The answer is not to retune because that's just shooting yourself in the foot. It's only compounded the problem!
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Norman Cook: I take back what I said. Dronfield is fed over the air from Chesterfield which is line-fed (phone line) from Emley.
Looking at the spread of the signal from the Dronfield transmitter I'm surprised you can receive it in Norton.
In any case, reception from Crosspool/Tapton Hill would give you all the channels.
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Darren: Communal aerial systems are often filtered so as to allow through channels that are used by the designated transmitter. Thus, when a new channel comes on air it might need adjustment.
When London Live comes on air in February then you might have the same issue.
Contact the party responsible such as your landlord.
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John Dyas: Reception of French channels suggests that there are lift conditions. I know we have had a lot of reports of issues with reception from all across the east of the country.
Perhaps it would be wise to wait and see if it starts to work again, with the suspicion that the conditions could be the cause of your issue.
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John Dyas: Your aerial is set vertically isn't it?
If not then this might explain the inconsistent strength on different channels. High power transmitters in France, which are those that at times might be available in the UK, are horizontally polarised, which makes me wonder if you have your aerial incorrectly set horizontally.
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trevor montgomery: No, not in the foreseeable future at least.
The new Sandy Heath HD mux will be co-channel with that of Hannington, so even if you used it you might find it wiped out at times. The power of the new mux from Crystal Palace is 36.3kW as against 200kW for the other six channels.
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trevor montgomery: Have you fitted aircraft warning lights on your aerial?
If you can receive the new multiplex (C33) from Crystal Palace then you could diplex your Hemel Hempstead aerial with it so as to use Hemel Hempstead for all viewing except the new HD mux.
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trevor montgomery: As you may be aware the cause of your difficulty with reception from Crystal Palace is the high ground at Bushey Heath and Stanmore Common, which is heavily tree-laden.
With this in mind, the use of a high-gain aerial is probably best not advised as it means that the "beam" width you're receiving across is narrower - it's that narrow angle which you're relying on for good quality. A lower gain aerial would provide a wider acceptance angle and therefore "poor" quality over a narrow part of its acceptance angle wouldn't deminish the quality of the signal coming down the lead as much (of course that isn't to say that it will be good enough).
The point is that with digital you have strength and quality. You can make the signal stronger by amplifying it but quality starts at the aerial.
I write these comments as a technical bod rather than an aerial installer. I have, however, taken this knowledge from one of the experts on here and it makes perfect sense.
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Gary k: Your aerial should point to the one you want to point it. There is no compulsion to use any particular transmitter!
The Bishop's Stortford relay transmitter carries only PSB (Public Service Broadcaster) channels, so you might like to use either Crystal Palace or Sandy Heath, if at all possible, so as to receive all channels.
It would appear that you are on the edge of the area served by the Bishop's Stortford transmitter and that you might potentially find the signal degraded at times due to interference from other high-power transmitters which use the same frequencies.
I suggest that the area that the Bishop's Stortford is intended to serve is that low-lying and near the river. This presumably has difficulty in achieving reliable reception from Crystal Palace.
Crystal Palace uses Group A channels exclusively and if your aerial is a Group A one (red tip) then it won't be suitable for Bishop's Stortford relay or Sandy Heath's COMs.
See:
Aerials, TV Aerial and Digital Aerial
Sandy Heath's PSBs are Group A and its COMs are top of Group B/bottom of C/D. Thus, for Sandy Heath an aerial spanning at least Group K is required.
For a list of PSB services and a list of COM services, see:
DTG :: DTT Services by Multiplex
Whilst Sandy Heath is only 24 miles away, line-of-sight is obstructed 13 miles away, due to the high ground around Therfield.
The effectivenes of yagi aerials on lower channels (frequencies) isn't as good on higher channels, so for Crystal Palace either use a log periodic or Group A yagi:
Crystal Palace Transmitter
You appear as if you might have line-of-sight to Crystal Palace (this excluding any obstruction on the ground such as buildings and trees):
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
The area between the yellow line and the pink one is known as the first Fresnel Zone. Objects within it can adversely affect reception. The ground from you up to Sawbridgeworth and the high ground around Epping Green are all within or near to it. For that reason, even though you have line-of-sight you could potentially have difficulty.
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Wednesday 11 December 2013 7:36PM
Barbara Hynes: The primary service area of Whittingslow transmitter is the Marsh Brook valley along which the A49 runs. The signal is beamed out from the 12 o'clock position (north) of the transmitter to the six o'clock position (south) - so it's not equal in all directions. Those in the valley are not sufficiently served by Sutton Coldfield because of the low-lying terrain and the higher ground in the way.
There is a two-tier terrestrial television transmitter network. Around 90% of the population can receive all channels, whilst the other 8.5% who can receive Freeview can only get the Public Service Broadcaster (PSB) channels; these are: BBC standard definition TV, BBC national radio, BBC One HD, BBC Two HD, BBC Three HD, CBBC HD, ITV, ITV HD, ITV+1, ITV2, Channel 4, Channel 4 HD, Channel 4+1, E4, Film4, More4 and Channel 5.
For that reason, even where reception may be easier from a local relay transmitter like Whittingslow, use of the main full-service transmitter like Sutton Coldfield might be preferred if there is a chance.
There are no available transmitters to your south. To get your bearings, the satellite dish points a little anti-clockwise of south.
I think that your aerial is most likely to point to Sutton Coldfield which is slightly anti-clockwise of east with the aerial set horizontally (elements flat).
If your aerial points to Whittingslow transmitter then it will be vertical (elements up/down).
If the engineer measured the strength of the signal from the aerial then why did he not look to resolve the issue, or at least offer a suggestion as to the problem?
An engineer on-site is best-placed to find the reason for the problem, and much better so than someone unconnected on an internet forum.
The most common reason for little or no signal is that there is an amplifier (booster) connected and which does not have mains electricity going into it.